Probably be worth looking into geting someone decent at micro-soldering to do the nistune install, could be cheaper than getting the workshop do do that part (especially if you can get a friend to do it).
QFM HPX or Remsa (Remsa pad sits inbetween HPX and A1RM) for a purely street driven car, QFM A1RM for a car that sees light track work, check GSL Rallysport's subsection on here.
Before the car is started with that Nistuned ECU, it would be best reverting back to a RB20 basemap (effectively overwritting whatever is loaded), then there is really 3 things you have to modify.
#1 MAF translation (I believe just a matter of selecting Z32 from a dropdown box).
#2 Resizing the injectors from stock to 550cc
#3 Finally injector lag time in microseconds ( http://www.nengun.com/sard/injectors says 0.85 millisec for your 550's, old Nistune required you to double this valve so you would enter 1700 microseconds or 850 microseconds if using a recent version of Nistune where you don't need to double the value).
In this state it would be drivable to the tuners, I just wouldn't drive it around like that unless AFRs were checked.
4 things I would check.
- Air flow meters (unplug them to confirm if it is or not)
- Faulty crank angle sensor
- Faulty coilpack ignitor (possibly has a poor ground)
- Faulty fuel pump (maybe blocked fuel filter)
Don't bother with piggyback's. Just get another stock ECU, R33 ECU's can't be Nistune'd so demand isn't very high so should be cheap to replace. If you ever did go Nistune you would need a Z32 ECU (VCT support) or a RB20 ECU (no VCT support) anyway.
I wouldn't go ahead and put a PFC in just incase what fried that ECU might fry another, until I was sure it was the ECU that was faulty and not something else electrical that caused it (water etc).
You mentioned (by a double post) that the car was sitting in some dudes backyard for ages... the fuel no doubt stale and octane booster wont do crap for it (only destroy your oxygen sensor). If it still does it with fresh fuel then read the sticky about the 4500-5500rpm misfire thread
Good gearbox with no know issues: Royal Purple Syncromax, Redline MT90, Motul Gear 300 (most expensive)
Good gearbox with minor crunch issue: Redline Shockproof Lightweight (very popular, I use it myself)
Rooted gearbox: Redline Shockproof Heavyweight
I'm not sure about Castrol to be honest, I've read people dropping their current oil for Castrol and it was worse than the old oil (some even putting the old oil back in)
Goes to show it's worth port matching the stock manifolds to the turbos, and here I was laughed at in a recent thread when I mentioned doing it in 350kw+ applications.
Pretty sure it's the same sensor, the factory water temp gauge is useless anyway. I've seen mine go over 105C at the track and it was still in the same position as 80C daily driving (needle in the middle).